[AArch64] Fix copy and paste error in tryCombineMULLWithUZP1() (NFCI) #97729
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The bitcast check was performed on the wrong value in one of the branches. I believe this doesn't actually result in any behavior difference, because the following code looking at ExtractHigh users doesn't try to look through BITCASTS. I've left a TODO for that. Fixes llvm#94761.
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@llvm/pr-subscribers-backend-aarch64 Author: Nikita Popov (nikic) ChangesThe bitcast check was performed on the wrong value in one of the branches. I believe this doesn't actually result in any behavior difference, because the following code looking at ExtractHigh users currently doesn't try to look through BITCASTS. I've left a TODO for that. Fixes #94761. Full diff: https://github.com/llvm/llvm-project/pull/97729.diff 1 Files Affected:
diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index e0c3cc5eddb82..760ae32d1059a 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -24829,7 +24829,7 @@ static SDValue tryCombineMULLWithUZP1(SDNode *N,
} else if (isEssentiallyExtractHighSubvector(RHS) &&
LHS.getOpcode() == ISD::TRUNCATE) {
TruncHigh = LHS;
- if (LHS.getOpcode() == ISD::BITCAST)
+ if (RHS.getOpcode() == ISD::BITCAST)
ExtractHigh = RHS.getOperand(0);
else
ExtractHigh = RHS;
@@ -24858,6 +24858,7 @@ static SDValue tryCombineMULLWithUZP1(SDNode *N,
// This dagcombine assumes the two extract_high uses same source vector in
// order to detect the pair of the mull. If they have different source vector,
// this code will not work.
+ // TODO: Should also try to look through a bitcast.
bool HasFoundMULLow = true;
SDValue ExtractHighSrcVec = ExtractHigh.getOperand(0);
if (ExtractHighSrcVec->use_size() != 2)
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davemgreen
approved these changes
Jul 5, 2024
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The bitcast check was performed on the wrong value in one of the branches.
I believe this doesn't actually result in any behavior difference, because the following code looking at ExtractHigh users currently doesn't try to look through BITCASTS. I've left a TODO for that.
Fixes #94761.